Sharp edge cutting die



Oct. 31, 1939. F. EXLEY 2,178,473

SHARP EDGE CUTTING DIE Filed March 9 1939 FIE-7: 5 E5. 10. 1% V 3 Q5 Patented Oct. 31, 1939 STAYS warn PATENT FFECE SHARP EDGE CUTTING DIE Application March 9, 1939, Serial No. 260,855

13 Claims.

This invention relates to improvements in sharp-edged cutting dies for blanking out various parts used in the assembly and manufacture of footwear or the like, from materials such as uncured, semi-cured, or completely cured rubber, crepe rubber, sponge rubber, felts, and fabrics, or in fact any materials of a soft and yielding nature.

The object of my invention is to overcome a fault in ordinary cutting dies known to the trade as undercutting, i. e'., the conditions wherein the cut blank has a contour, shape, or area on one side which does not coincide with the contour, shape or area of the other side. Such fault or defect, as is well known, arises from the fact that materials of comparatively soft nature will yield and will be initially compressed below the cutting edge of the die before said edge actually enters the material, the degree or depth of such compression varying with the density or hardness of the material. The material directly under and adjacent to the compressed area is obviously distorted and displaced, and when the cutting edge of the die passes entirely through the material 5 and the pressure removed, a reaction takes place during which the displaced portion of the material returns to its original and normal shape relative to the balance of the mass, and invariably the area of the blank which was in contact with the cutting block is found to be of less area than the side into which the die entered, and the out side edges of the blank are not found to be normal to the top and bottom surfaces thereof, but are found to slant at an angle to the cutting block or in some cases the cut edges are concaved. The above fault occurs regardless of the size or shape of the die, and regardless of whether cutting is eifected by slow pressure or by a quick striking movement; and no amount of variation in the design or angle of the cutting edge of the die will overcome the above fault.

My improved cutting die hereinafter described entirely overcomes and eliminates undercutting, due to incorporation therein of a yieldable presser strip supported and guided by bolts, rivets, or studs which are mounted on a flange attached to the die; and my die is particularly adapted for cutting rubber of considerable thickness, or other soft readily yielding material.

I will explain the invention with reference to the accompanying drawing which illustrates one practical embodiment thereof to enable others familiar with the art to adopt and use the same; 55 and will summarize in the claims the novel features of construction, and novel combinations of parts, for which protection is desired.

In said drawing:

Fig. 1 is a sectional view showing the cutting edge of an ordinary die about to enter a sheet of soft mate-rial of substantial thickness.

Figs. 2 and 3 indicate the shape of blanks of such material cut by ordinary dies.

Fig. 4 is a bottom plan view of an ordinary combined rubber sole and heel blank of the type operated upon by such dies.

Fig. 5 is a side elevation showing an ordinary die in cutting position on a combined sole and heel blank, such as shown in Fig. 4.

Fig. 6 is a side elevation of my novel cutting die applied to the sole and heel blank shown in Fig. 4.

Fig. 7 is an enlarged top plan View of the die shown in Fig. 6, detached.

Fig. 8 is a transverse section on line 88, Fig. 7.

Figs. 9, 10 and 11 are views indicating the operation of the presser strip of my novel die during the actual cutting of a blank.

Fig. 12 shows a blank cut by my novel die.

Fig. 13 shows a die according to my invention for cutting heel blanks, in which the presser strip extends entirely around the cutting edge.

Fig. 14 is a transverse section on the line l4l4, Fig. 13.

Figs. 15 and 16 are plan views showing other forms of dies in which the presser strip extends entirely around the cutting edge.

As shown in Figs. 1 to 3, when the cutting edge A of an ordinary die enters a relatively thick piece of soft material, such as crepe rubber B, the material directly under the blade is initially compressed as at B to a considerable extent before blade A actually starts to sever the material, and therefore the cut edge, after the material has resumed its normal shape, will not be normal to the cutting block but will either be beveled inwardly as at B2 in Fig. 2, or will be of concave shape as indicated at B3 in Fig. 3. This defect is generally known to the trade as undercutting. No amount of alteration in the design or angle of the cutting edge will overcome the above defect.

In order to obviate undercutting I provide the heel end to of the die 1 (Figs. 6-11 inclusive) with. an outwardly extending flange E?) at the upper edge for supporting a presser strip 2, said flange being provided on its underside with spaced series of studs 3 having heads on their lower ends; and on said studs is slidably mounted the horizontal flange of a presser strip 2 which strip is shown as being substantially L-shaped in cross-section, and having a narrow vertical wall normally terminating somewhat below the lower cutting edge lac of the die, springs 4 on studs 3 being interposed between the flange lb and the horizontal flange of presser strip 2, to yieldably maintain the presser strip normally in the position shown in Fig. 8, the springs being of such strength that they will hold the presser strip in such relative position with respect to the cutting edge lac at the beginning of the cutting stroke, and will exert a constantly increasing pressure on the material as the die progresses through said stroke. The lower edge of presser strip 2 is spaced from and parallel with the cutting edge I12 of the die, and extends around the entire heel portion la of the die as clearly indicated in Figs. 6-8 inclusive. Other means for yieldably mounting the presser strip on the die may be provided.

Fig. 9 shows a cross-section in which the presser strip 2 of the die is merely resting normally upon the material B to be cut, and the cutting edge lac is supported by strip 2 above and away from the material. Fig. 10 shows the relative positions of parts after the usual die striking arm (not shown) has come into contact with the back of the die and has partly depressed the die so that presser strip 2 has started to initially compress the material B before the cutting edge lrc of the die has actually commenced to sever the material. Fig. 11 shows the cutting edge Izc of the die partly severing the material, and shows the presser strip 2 further depressed into the material by action of springs 4, the strip 2 equalizing pressures within the material adjacent the cut so that the cut edge in the severed material B will be normal to the top and bottom surfaces of the material resulting in a cut blank Bx (Fig. 12) having perpendicular side edges. Having once determined the strength of springs 4 to produce the requisite equalizing pressure, the die will operate perfectly on a wide range of materials, from the thickest to the thinnest, and will constantly produce blanks having straight-cut edges normal to the cutting block.

In Figs. 911 the lower edge of presser strip 2 is indicated as being relatively blunt, however a blunt edge is not an essential as a somewhat sharper edge on the presser strip such as shown in Fig. 14 may be used, and same operates as efiectively as a blunt edge provided the strip is equipped with Weaker or lighter springs 4 than used when strip 2 has a blunt edge. The strength of springs 4 is thus proportional to the width of the lower edge of the strip 2, weaker or lighter springs being required when strip 2 has a sharpened edge, and greater spring strength being required when the thickness or bluntness of the edge of strip 2 is increased. The same conditions also apply with regard to the proximity of strip 2 in relation to the cutting edge la: of the die; for when presser strip 2 is located farther away from the cutting edge Ir, greater spring compression or strength is required than when same is positioned nearer the cutting edge In. The advantage however of using a blunt edged strip 2 is the saving in the cost of manufacturing the die, as a sharpened edge strip is in fact a blunt edged strip which has been processed one step further, at additional cost.

I am aware that it has heretofore been attempted to make dies to correct undercutting by incorporating therein an additional or second fixed cutting edge located in approximately the same relative position as my yielding presser strip 2. Such dies have been reasonably effective in correcting this fault, but they have serious and potent disadvantages in that same are difiicult and expensive to manufacture, and the same skill and care must be exercised in producing the secand edge as is required to produce the die itself, and furthermore the proximity of the second edge of the main edge makes it difiicult to sharpen and file the edge after the second edge is attached. A further disadvantage is that the above doubleedge construction is limited to a relatively small portion of the die, since to entirely surround a die with a second edge would be to form in effect a die within a die, and such construction is obviously impractical. In addition to the difilculty of sharpening above mentioned, distortion and warping in heat treatment must also be taken into consideration; and furthermore the outer ring out from the stock by the second edge has been found to wedge between the two cutting edges and must be picked out by hand, slowing up operation to such an extent that labor costs are prohibitive.

The advantage of my construction lies in the fact that the die is made in the usual way, and the flange lb is then attached to the back or striking end and therefore does not interfere in any way with the customary and regular operations of grinding, polishing, and filing. The presser strip 2 is made separately from a separate template, and is attached to the die at any time it is convenient; furthermore, the strip 2 may be detached at any time and the die used as an ordinary die on material not susceptible to undercutting. My dies are easy to construct, easy to maintain, and easily and quickly converted from the standard conventional type to the new and improved type as herein described.

Unlike the above mentioned double-edged dies, my presser strip 2 is not limited to any portion of the die, and due to my method of construction and attachment, I may entirely surround the periphery of the die with a presser strip 2, which will be found desirable in some cases. For instance, in the production of rubber heel blanks I use dies such as shown in Figs. 13 and 14 in which the die I 0 is completely surrounded by the presser strip l2. If it were possible to construct a double-edge die to cut patterns similar to that shown in Figs. 13-14, the disadvantages above enumerated in making and using such dies would still obtain and would make use thereof impractical and prohibitive. Figs. 15 and 16 represent other contours of dies 20 completely surrounded by continuous presser strips 22.

Furthermore, combined sole and heel blanks C are usually in the form shown in Figs. 4 and 5 in which the heel portion C is of considerably greater thickness than the sole portion C2 which latter portion moreover may be provided with anti-slipping ribs C3 or other raised surfaces. When an ordinary die such as A (Fig. 5) is placed in cutting position on blank C, obviously such die will be tilted upon the blank as indicated in Fig. 5. The defect of undercutting is particularly marked in connection with blanks of this type, due to the greater thickness of the heel portion C as compared with the sole portion C2, accentuated by the fact that when the die A is placed on the blank C ready for the cut, the sole portion C2 pitches forwardly presenting the heel and toe of the die to the material in such a way that the cutting edge is not disposed horizontally. To overcome this further fault in positioning and locating the cutting die on the blank C, and in order to properly support the toe portion is, I provide an effective arrangement which forms a part of my improved die construction which will support the front portion is of the die 5 on the combined sole and heel blank C so that the die will rest normally level thereon.

At the toe portion is of the die I provide a lug l preferably welded to the outside of the die. However, one or more such lugs may be disposed at any place or places where support is desired, and the lug or lugs it may be placed either outside or inside the die. As shown, lug It is located some distance down from the back or striking edge of the die, and is provided with a hole iu parallel to the wall of the die, said hole being slightly larger than the post iv so that said post will slide freely therein, said post having heads on both ends confining same within the hole. A sprin lw is provided on post to interposed between the lower head and the bottom of lug it, said spring being comparatively weak as it need exert only suflicient force to support the comparatively light weight of the die to hold same parallel with the cutting block as shown in 6. The post in only supports the die 8 in the desired position until, on the downward motion of the striking arm, the entire upper or striking edge of the die comes in contact with the striking arm which latter carries the die downwardly through the stock, so that the cutting edge ix will at all times be held parallel with the cutting block. Ordinarily one such post to as above described is sufiicient when such support is located in the center of the toe portion is of a die. However, any number of supports may be used and may be located at various places to suit conditions. The over-all length of post Iv should be less than the height of die 5 so that the upper head of the post will not contact the die striking arm and cause the other end of the die to be depressed into the blank C.

I claim:

1. A sharp edge cutting die comprising a blade having a cutting edge and a striking edge; a presser strip yieldably mounted on said blade and having a narrow edge normally extending below and parallel with the cutting edge of the blade; and means for yieldably maintaining the presser strip in normal position, said means causing the presser strip to exert a constantly increasing pressure on the material being cut by the die as the blade progresses thr ugh said material.

2. A sharp edge cutting die comprising a blade having a cutting edge and a striking edge; a flange on said blade adjacent the striking edge; studs projecting from the lower face of the flange; a presser strip slidably mounted on said studs and having a narrow edge normally extending below and parallel with the cutting edge of the blade; and means for yieldably maintaining the presser strip in normal position, said means causing the presser strip to exert a constantly increasing pressure on the material being out by the die as the blade progresses through said material.

3. In a die as set forth in claim 2, said presser strip having a flange perforated to receive the studs; and means on the studs for limiting the downward movement of the strip.

4. In a die as set forth in claim 2, said presser strip having a flange perforated to receive the studs; means on the studs for limiting the downward movement of the strip; and said yieldable means comprising expansible members interposed between the flange of the strip and the flange of the blade.

5. A sharp edge cutting die comprising an endless contour cutting blade conforming with the shape of the desired blank and having a cutting edge and a striking edge; a presser strip yieldably mounted on said blade and having a relatively blunt narrow edge normally extending below and parallel with the cutting edge of the blade; and means for yieldably maintaining the presser strip in normal position, said means causing the presser strip to exert a constantly increasing pressure on the material being cut by the die as the blade progresses through said material.

6. A sharp edge cutting die comprising an-endless contour cutting blade conforming with the shape of the desired blank and having a cutting edge and a striking edge; an external flange around the die adjacent the striking edge; studs projecting from the lower face of the flange; a presser strip slidably mounted on said studs and having a relatively blunt narrow edge normally extending below and parallel with the cutting edge of the blade; and means for yieldably maintaining the presser strip in normal position, said means causing the presser strip to exert a constantly increasing pressure on the material being cut by the die as the blade progresses through said material.

'7. In a die as set forth in claim 6, said presser strip having a flange perforated to receive the studs; and means on the studs for limiting the downward movement of the strip,

8. In a die as set forth in claim 6, said presser strip having a flange perforated to receive the studs; means on the studs for limiting the downward movement of the strip; and said yieldable means comprising coiled springs on the studs interposed between the flange of the strip and the external flange of the die.

9. A sharp edge cutting die for operating on combined sole and heel blanks, comprising an endless contour cutting blade conforming with the shape of the finished sole and heel and having a cutting edge and a striking edge; a presser strip yieldably mounted on said blade and having a relatively blunt narrow edge normally extending below and parallel with the cutting edge around the heel portion of the blade; and means for yieldably maintaining the presser strip in normal position, said m ans causing the presser strip to exert a constantly increasing pressure on the material being cut by the die as the blade progresses through said material.

10. In combination with a die as set forth in claim 9, an external flange around the heel portion of the blade adjacent the striking flange;

a series of studs projecting from the lower face of the flange; said presser strip having a flange perforated to receive the studs; means on the studs for limiting the downward movement of the strip; and said yieldable means comprising expansible members interposed between the flange of the strip and the external flange of the blade.

11. A cutting die comprising an endless contour cutting blade having a cutting edge and a striking edge; a presser strip yieldably mounted on said blade and having a narrow edge normally extending below and parallel with the cutting edge, said presser strip extending around a portion of the blade; means for yieldably maintaining the presser strip in normal position; and means for leveling the die on the blank.

12. A cutting die comprising an endless contour cutting blade having a cutting edge and a striking edge; a presser strip yieldably mounted on said blade and having a narrow edge normally extending below and parallel with the cutting edge, said presser strip extending around a portion of the blade; means for yieldably maintaining the presser strip in normal position; and a lug on the blade substantially diametrically opposite the presser strip and having a vertical bore; a post slidably confined in said bore and normally projecting below the cutting edge; and means for yieldably maintaining the post in normal position.

13. A cutting die comprising an endless contour cutting blade having a cutting edge and a striking edge; a presser strip yieldably mounted on said blade and having a narrow edge normally extending below and parallel with the cutting edge, said presser strip extending around a portion of the blade; means for yieldably maintaining the presser strip in normal position; and a lug on the blade substantially diametrically opposite the presser strip and disposed intermediate the cutting and striking edges and having a vertical bore; a post of less height than the blade slidably confined in said bore and normally projecting below the cutting edge; and means for yieldably maintaining the post in normal position.

LEO F. EXLEY. 

